Scanning electron microscopes (SEMs) are known in the art. Typical prior art SEMs include at least one detectors for providing SEM images. U.S. Pat. No. 5,659,172 of Wagner describes a method for reliable defect detection using multiple perspective SEM images.
A SEM usually includes an electron gun for generating an electron beam, a SEM lens system for focusing and converging the electron beam, a deflection coil for deflecting the electron beam, a detector for detecting electrons, such as secondary emitted electron or reflected electrons that are emitted/ reflected from an inspected object and a processor that is operative to construct SEM images in response to detection signals provided from the detector.
Focused ion beam (FIB) systems are known in the art. FIB systems are generally utilized to perform die milling and cross sectioning. The milled or cross sectioned die is usually analyzed to detect defects. FIB systems can also be utilized to generate FIB images.
FIB systems usually include an ion source for generating an ion beam, a FIB lens system for focusing the ion beam to provide a focused ion beam and an ion beam deflector for deflecting the focused ion beam. Typically, a broad ion beam is utilized for an initial milling step, while a narrower ion beam is utilized for a successive step of polishing the walls of the cross sectioned wafer.
A FIB system that is operative to generate a FIB image also has a detector and a processor. Usually, the ion source, the FIB lens system and the ion beam deflector are located within a column that is commonly referred to as FIB column. The detector can also be placed within the FIB column.
There are various prior art systems that include both SEM columns and FIB columns, one being the SEMVision G2 of Applied Materials, Inc. of Santa Clara Calif.
FIB milling, SEM milling usually include injecting gas that interacts with the beam of charged particles (ions in the case of FIB, electrons in the case of SEM). The interaction accelerates and in some cases even facilitates the milling.
Gas may also be injected in order to reduce charging effects that may deteriorate a SEM image.
Gas is injected by a gas conduit that is made of a conductive material. The gas conduit usually effects the trajectory of the beam of charged particles. This phenomenon is also known as interaction with the electrons optic. Said phenomenon may result from the presence of a nozzle at one side of the beam, but not at the other side and may result from temporary charging of the gas conduit by charged particles that are scattered/ returned from the specimen.
U.S Pat. No. 6,555,815 of Feuetbaum et al. titled “Apparatus and method for examining specimen with a charged particle beam” provides an apparatus for examining a specimen with a beam of charged particles, where charging of the specimen is avoided or reduced by injecting inert gas onto the sample's surface. In order to avoid interactions with the electron optics, various embodiments are disclosed for providing a rotationally symmetrical nozzles and/or electrodes. Additionally, embodiments are disclosed wherein a plurality of gas conduits are arranged in a rotationally symmetrical manner. Alternatively, the conduit is incorporated into an element of the electron optics, such as the magnetic lens. Also, in order to reduce or eliminate interaction of the electrons with the gas molecules, embodiments are disclosed wherein the gas is pulsated, rather than continually injected.
There is a further need to provide efficient apparatuses and methods for providing gas to a specimen.